It's an old 89 Toyota pickup so not a lot of electronics.
Apparently something's in there - " I have horrible noise coming through the radio from the engine (when I push the accelerator)"
That year is well past the point OBD I was implemented, so there's a computer in there somewhere.
Try different antenna combinations and see. Easy/cheap enough to do. An external antenna adds separation distance and the body will help act as a shield.